1. Field of the Invention
The present invention relates to a laser-scanning microscope used in fluorescence examination or confocal fluorescence examination in applications such as imaging and the study of cellular function.
2. Description of Related Art
In the related art, a laser-scanning microscope is a known apparatus for examining cellular function and so on. Such an apparatus functions by irradiating a specimen, such as a living organism, with excitation light from the surface thereof and selectively detecting fluorescence emitted from a position at a predetermined depth in the specimen. (See, for example, Japanese Unexamined Patent Application Publication No. HEI-3-87804 (page 2, etc.) and Japanese Unexamined Patent Application Publication No. HEI-5-72481 (FIG. 1, etc.).)
In addition to standard microscope examination, this laser-scanning microscope can obtain images by scanning laser light converged onto a minute spot on the specimen with a scanning unit such as galvano mirrors or the like and detecting the fluorescence emitted by the specimen.
This laser-scanning microscope affords an advantage in that, since the minute spot allows excellent resolving power and light outside the minute spot can be eliminated, it is possible to obtain sharp observation images with a high signal-to-noise ratio.
However, the known laser-scanning microscope suffers from the drawback that the size of the apparatus is large because, in addition to optical systems for standard fluorescence observation, such as an objective lens and an imaging lens, it is also necessary to include optical systems such as a pupil projection lens and a scanning mechanism.
In general, therefore, the optical system of the laser-scanning microscope has an objective lens focal length of approximately 180 mm. As a result, the overall length from the specimen to the scanning mechanism located close to the conjugate position of the pupil of the objective lens is 400 to 500 mm, which makes the overall size of the apparatus relatively large.
Accordingly, to allow confocal fluorescence examination or fluorescence examination, the specimen must be positioned on a stage of the microscope. In practice, therefore, when carrying out in-vivo fluorescence examination of cells or small animals such as rats under incubation conditions, there is a restriction in that a suitable examination environment must be created on the stage.
Furthermore, the laser-scanning microscope is generally constructed so that examination is carried out in a state where the optical axis of the objective lens is orthogonal to the surface of the stage. As a result, it is difficult to carry out examination from an oblique direction with respect to the specimen. Also, it is difficult to carry out examination while the main body of the laser-scanning microscope is tilted with respect to the specimen or while the specimen or the stage is tilted.